Low Voltage Stereo Amplifier

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thedarkness3300

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Hey guys, I'm currently doing a diploma lab project ( Low Voltage Stereo Amplifier ) in the figure above. When point 1 and 8 of the IC LM386N is connected together, I have found out that there is a lot of noise when songs are playing through speaker. Can you all give me some suggestion how to reduce the noise but the sound is still amplified? Thanks alot !!
 

Hello,

when you short 1 and 8 with capacitor, the gain increases to 200. reduce your gain by adding a resistor in series (see application hints in the datasheet). you should select the gain such that with the input potentiometer full, your output doesn't clipp.

also make sure that your supply is clean. you can test this by feeding the circuit from a 12V (car) battery (make sure you have a fuse connected at the 12V battery).

What is the level of the source's (output voltage)?
 

Something to think about - check all earths are going to a single point, check there are no earth loops, make sure the input/pot earth to central earth point is independent of power supply earth up to the central earth point, and the speaker earth up to the central earth point ..
So, star all the earths off from a single point on the PCB, making sure there are no extra earth paths ..

IanP
:|
 

Like I said on the other website, if the gain is too high then the amplifier IC amplifies its own noise.
Are you sure it is noise (hiss) and not severe clipping distortion (buzzing sounds)?

The LM386 is cheap and noisy. Keep its gain at only 20 then use a low noise opamp as a preamp with a gain of 10.
 

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